1. Technical Field
The invention relates to anchors which are intended for installation in bodies of a softer material than the anchors, such as plastic, for subsequently receiving an attachment fastener for securing the body to another component. More particularly, the invention relates to such an anchor which has increased resistance to axial pullout and to rotation once inserted into an object.
2. Background Information
Various types of anchors have been developed which are mounted in objects or various types of bodies for securing the object or body to another component, or for securing other components to the object, by means of a fastener which extends into a threaded opening formed in the center of the anchor. Most of these anchors are used in objects that are formed of materials which do not provide sufficient resistance for holding a fastener in position without the use of such an anchor, in order to mount the object on a supporting structure or the like. Most known anchors when used with plastic components or similar soft materials, are molded into the object when the object is formed, and are provided with some type of knurled or fluted surface to secure it in position. Although some of these prior art anchors perform satisfactory, they require that they be inserted into the plastic object or body during molding, or they are secured in position by sonic welding or with an adhesive, all of which increase the cost of manufacture. Likewise, most of these anchors are of a rounded configuration and are subject to rotation in the object or body in which they are mounted, when an excessively large torquing force is applied thereto, especially when the attachment fastener is inserted and screwed therein.
Other types of anchors are adapted to be snapfitted through openings formed in an object, as opposed to insertion into a solid body. It is more difficult to retain the anchor in an aperture formed in a solid body in contrast to those anchors which extend through openings formed in a plate or other support.
Examples of known prior art anchors are shown in the following patents.
U.S. Pat. No. 2,836,214 discloses a plastic insert or anchor having a generally rectangular cross-sectional configuration so that when it is inserted into an opening it will lock itself in position. It is provided with a plurality of sloped surfaces which resist pullout once inserted into the opening of the plate.
U.S. Pat. No. 2,984,698 discloses an anchor grommet having a square surface to prevent rotation once it is inserted into a hole in a relatively flat plate. The tapered surfaces resist outward axial movement once inserted into the hole. It also is provided with a circular central opening for receiving a mounting bolt or other fastener therein.
U.S. Pat. No. 3,756,116 discloses another plastic grommet or anchor insert is adapted to be inserted through an opening in a flat plate and which has protuberances on the sidewalls thereof to prevent extraction of the insert once inserted through the plate opening.
U.S. Pat. No. 3,803,973 discloses a plastic insert or anchor that has a generally square configuration and has tapered sidewall structures to hold the insert in a complementary shaped opening in a plate once it is inserted therein. This anchor also has a circular central opening for receiving an attachment fastener.
U.S. Pat. No. 3,830,134 discloses another plastic anchor generally square in configuration, that once inserted into a complementary shaped opening in a plate, it locks itself in position due to the resilience of the material as opposed to the use of ribs or barbs. This anchor also is adapted to receive a fastener through a central opening thereof.
U.S. Pat. No. 4,077,300 discloses a plastic grommet having a square outer configuration and a central hole for receiving a fastener. Projections formed on the outer surface function as retaining members after the grommet is inserted through a complementary shaped hole in the mounting plate.
U.S. Pat. No. 4,842,462 is believed to be the closest known fastening anchor or insert to the present invention. It discloses a body that is made of metal having a flat to prevent rotation thereof after mounting in an object. However, this insert must be either molded into the plastic object, or sonically or thermally welded into the plastic after molding. It is not forcibly pushed into the object after molding as is the anchor of the present invention, and it would require additional equipment and manufacturing operations to install the same.
Accordingly, none of the known prior art anchors are adapted to be forcibly inserted into an opening of a solid body formed of a softer material than the anchor, and which is able to resist greater axial pullout forces and rotational forces once forcibly inserted into position in the body.